Activated Carbon as a Bone Substitute: Enhancing Mechanical and Morphological Properties in a Rat Tibia Defect Model

Abstract

Activated carbon (AC), a highly porous and low-cost material, was tested as a biosubstitute material for healing bone defects. The aim of this work was to investigate the use of 4 different activated carbon materials in the tissue repair process, verifying morphological and biomechanical aspects of the bone. Experiments were performed by drilling rat tibias and filling the resultant bone cavities with four kinds of ACs (AC1, 2, 3 e 4). A Control group (CTL) and untreated lesion group (NT) were also included. The efficiency of the repair was evaluated after 30 days. No alteration of hepatic and renal activity was found, both by histological evaluation of those organs and by the levels of SGOT/SGTP and urea. An increase in ALP levels was observed in the NT group, while all the groups with ACs maintained this enzyme close to the values of the CTL group. The histological study of bone was carried out to evaluate the organization of the formed bone tissue, compared with the quality of repair after treatment. The biomechanical properties (Maximal Force = Fmax and Maximal Deformation = Dmax) of bone were evaluated by three-point flexural tests. The NT group presented immature bone tissue and, although the AC1, AC2 and AC3 groups presented granulation tissue, indicating a delay in bone organization, the Fmax values maintained similar to the NT group. Group AC4 showed mechanical properties and tissue organization similar to the CTL group. Activated carbons allow tissue growth in a rat tibial bone defect model. However, the specific structural characteristics of ACs are important and may contribute to a better organization of bone tissue, since AC4 presented better histological and biomechanical results than AC1, AC2 and AC3 materials. In conclusion, the activated carbon AC4 (Norit ROX0.8) enabled organized bone growth with mechanical properties similar to the normal tissue CTL, in a rat tibial bone defect model. The superior performance of AC4 may be related to its structural characteristics.